Drivers: hv: vmbus: Export hv_vmbus_exists() and use it in pci-hyperv

With commit f84b21da3624 ("PCI: hv: Don't load the driver for baremetal root partition"),
the bare metal Linux root partition won't use the pci-hyperv driver, but
when a Linux VM runs on the Linux root partition, pci-hyperv's module_init
function init_hv_pci_drv() can still run, e.g. in the case of
CONFIG_PCI_HYPERV=y, even if the VMBus driver is not used in such a VM
(i.e. the hv_vmbus driver's init function returns -ENODEV due to
vmbus_root_device being NULL).

In such a Linux VM, init_hv_pci_drv() runs with a side effect: the 3
hvpci_block_ops callbacks are set to functions that depend on hv_vmbus.

Later, when the MLX driver in such a VM invokes the callbacks, e.g. in
drivers/net/ethernet/mellanox/mlx5/core/lib/hv.c:
mlx5_hv_register_invalidate(), hvpci_block_ops.reg_blk_invalidate() is
hv_register_block_invalidate() rather than a NULL function pointer, and
hv_register_block_invalidate() assumes that it can find a struct
hv_pcibus_device from pdev->bus->sysdata, which is false in such a VM.

Consequently, hv_register_block_invalidate() -> get_pcichild_wslot() ->
spin_lock_irqsave() may hang since it can be accessing an invalid
spinlock pointer.

Fix the issue by exporting hv_vmbus_exists() and using it in pci-hyperv:

    hv_root_partition() is true and hv_nested is false ==>
	hv_vmbus_exists() is false.

    hv_root_partition() is true and hv_nested is true ==>
	hv_vmbus_exists() is true.

    hv_root_partition() is false ==> hv_vmbus_exists() is true.

While at it, rename vmbus_exists() to hv_vmbus_exists() to follow the
convention that all public functions have the hv_ prefix; also change
the return value's type from int to bool to make the code more readable;
also move the two pr_info() calls.

Reported-by: Mukesh Rathor <mrathor@linux.microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 3d1a58b667dbb98bc740f641d8691419dac0b7be..24fa0b2443c3e6c3d02ddfe3800a0cb1c672698e 100644 (file)
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -101,13 +101,11 @@ struct device *hv_get_vmbus_root_device(void)
 }
 EXPORT_SYMBOL_GPL(hv_get_vmbus_root_device);
 
-static int vmbus_exists(void)
+bool hv_vmbus_exists(void)
 {
-       if (vmbus_root_device == NULL)
-               return -ENODEV;
-
-       return 0;
+       return vmbus_root_device != NULL;
 }
+EXPORT_SYMBOL_GPL(hv_vmbus_exists);
 
 static u8 channel_monitor_group(const struct vmbus_channel *channel)
 {
@@ -1577,11 +1575,10 @@ int __vmbus_driver_register(struct hv_driver *hv_driver, struct module *owner, c
 {
        int ret;
 
-       pr_info("registering driver %s\n", hv_driver->name);
+       if (!hv_vmbus_exists())
+               return -ENODEV;
 
-       ret = vmbus_exists();
-       if (ret < 0)
-               return ret;
+       pr_info("registering driver %s\n", hv_driver->name);
 
        hv_driver->driver.name = hv_driver->name;
        hv_driver->driver.owner = owner;
@@ -1607,9 +1604,8 @@ EXPORT_SYMBOL_GPL(__vmbus_driver_register);
  */
 void vmbus_driver_unregister(struct hv_driver *hv_driver)
 {
-       pr_info("unregistering driver %s\n", hv_driver->name);
-
-       if (!vmbus_exists()) {
+       if (hv_vmbus_exists()) {
+               pr_info("unregistering driver %s\n", hv_driver->name);
                driver_unregister(&hv_driver->driver);
                vmbus_free_dynids(hv_driver);
        }

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 49c0a2d51162a207b46e2ef3f73fecc973a91ff1..cfc8fa403dad66d0d74e369433df130ee5de3573 100644 (file)
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -4172,7 +4172,7 @@ static int __init init_hv_pci_drv(void)
        if (!hv_is_hyperv_initialized())
                return -ENODEV;
 
-       if (hv_root_partition() && !hv_nested)
+       if (!hv_vmbus_exists())
                return -ENODEV;
 
        ret = hv_pci_irqchip_init();

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index dfc516c1c7193fb2d12d1097bf5486ee79bef239..5459e776ec17517a649787b30bde7ed02024e5c5 100644 (file)
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1304,6 +1304,8 @@ static inline void *hv_get_drvdata(struct hv_device *dev)
 
 struct device *hv_get_vmbus_root_device(void);
 
+bool hv_vmbus_exists(void);
+
 struct hv_ring_buffer_debug_info {
        u32 current_interrupt_mask;
        u32 current_read_index;